//这个action以Async结尾，并且返回值是void
        public void TestAsync()
        {
            //实现异步action加计数1
            AsyncManager.OutstandingOperations.Increment();
            FileStream fileStream = new FileStream(@"C:\Users\wuxq\Documents\Visual Studio 2010\Projects\MvcAppDemo2\AsyncControllerDemo\并发控制.txt", FileMode.Open);
            byte[] byteArray = new byte[fileStream.Length];
            fileStream.BeginRead(byteArray, 0, (int)fileStream.Length, (IAsyncResult result) =>
            {
                string content = Encoding.Default.GetString(byteArray);
                //参数要放在这个字典里面实现向Completed action传递
                AsyncManager.Parameters["content"] = content;
                //异步action回调结束
                AsyncManager.OutstandingOperations.Decrement();
                fileStream.Close();
            }, null);
        }

        //这个action以Completed为后缀异步action结束后调用的函数，返回值为ActionResult
        public ActionResult TestCompleted(string content)
        {
            Response.Write(content);
            return View();
        }